Logical zone table generation process and apparatus

ABSTRACT

A disc-drive system and method for generating logical zones that each have an approximate number of spare sectors, and that are used to translate logical block addresses. A disc drive includes a disc-drive housing and a disc assembly mounted to rotate within the housing. A transducer is positionable to transduce data to and from first, second and third zones. An address translator translates a logical block address to a position address. A controller is operable to control positioning of the transducer based on the position address, wherein a first predetermined number of spare sectors are allocated to the first zone, and a second predetermined number of spare sectors are allocated to the second zone and third zone combined. Some embodiments further include a logical zone table, wherein each logical zone includes one or more zones based on a number of defects found in each zone, in order that each logical zone includes a similar number of defects.

RELATED APPLICATIONS

[0001] This application claims the benefit under 35 U.S.C. 119(e) ofU.S. Provisional Application Serial No. 60/239,981 filed Oct. 13, 2000.

FIELD OF THE INVENTION

[0002] The present invention relates to the field of mass-storagedevices. More particularly, this invention relates to a method andapparatus for generating logical zones that each have an approximatenumber of spare sectors, and that are used to translate logical blockaddresses.

BACKGROUND OF THE INVENTION

[0003] Disc-drive devices that store massive amounts of data are keycomponents of computer systems. A disc drive typically includes a discassembly having at least one disc that is rotated, an actuator thatmoves a transducer to various locations over the rotating disc, andcircuitry that is used to write and/or read data to and from the discvia the transducer. The disc drive also includes circuitry for encodingdata to be written to the disc so that it can be successfully retrievedfrom the disc and decoded. A microprocessor is typically used to controlmost operations within the disc drive, and to transmit read data to anexternal computer (or information processing system) and receive datafrom the external computer to write to the disc.

[0004] The disc drive includes a transducer for writing data ontocircular or spiral tracks in a magnetic layer on the disc surfaces andfor reading the data from the magnetic layer. In some drives, thetransducer includes an electrically driven coil (or “write head”) thatprovides a magnetic field for writing data, and a magneto-resistive (MR)element (or “read head”) that detects changes in the magnetic fieldalong the tracks for reading data. Each disc surface is typicallyallocated into a number of concentric circular tracks and data is storedalong these tracks as individual magnetized patterns along the track.The transducer having a flux path and a gap is used to magnetize thetrack. The gap is passed near the disc. By changing the magnetic fluxpassing across the gap, individual portions of the track are magnetized.The same transducer is also used to read the data from the disc. Sometransducers include a electromagnetic coil write head and amagneto-resistive read head.

[0005] The transducer is typically placed on a small ceramic block, alsoreferred to as a slider, that is aerodynamically designed so that itflies over the disc. The slider is passed over the disc in a transducingrelationship with the disc. Most sliders have an air-bearing surface(“ABS”) which includes rails and a cavity between the rails. When thedisc rotates, air is dragged between the rails and the disc surfacecausing pressure, which forces the head away from the disc. At the sametime, the air rushing past the cavity or depression in the air bearingsurface produces a negative pressure area. The negative pressure orsuction counteracts the pressure produced at the rails. The slider isalso attached to a load spring which produces a force on the sliderdirected toward the disc surface. The various forces equilibrate so theslider flies over the surface of the disc at a particular desired flyheight. The fly height is the distance between the disc surface and thetransducing head, which is typically the thickness of the airlubrication film. This film eliminates the friction and resulting wearthat would occur if the transducing head and disc were in mechanicalcontact during disc rotation. In some disc drives, the slider passesthrough a layer of lubricant rather than flying over the surface of thedisc.

[0006] Encoded information representative of data is stored on thetracks on the surface of the disc. A transducer, (read/write headsattached to a slider), is typically located on each side of each storagedisc, and reads or writes information on the disc surface when thetransducer is accurately positioned over one of the designated tracks onthe surface of the storage disc. The transducer is moved to and heldover a target track based on servo information read from the discsurface. As the storage disc spins and the read/write head is accuratelypositioned above a target track, the write head serially stores dataonto a track by magnetically writing encoded information representativeof data onto the storage disc. Similarly, reading data on a storage discis accomplished by positioning the read head above a target track andreading the stored material on the storage disc. To write on or readfrom different tracks, the read/write head is moved radially across thetracks to a selected target track.

[0007] During manufacture, servo information is encoded on the disc todefine tracks, and is subsequently used to accurately locate thetransducer on these tracks to write and read data. Some drives use adedicated servo surface to define tracks for all the other discsurfaces, while modem disc drives typically use embedded servo signals,where every disc surface includes its own servo information interspersedwith data information. The written servo information is used duringnormal write and read operations to locate the actuator and its armassembly and transducer head(s) at the required position on the discsurface and hold them very accurately in position during a read or writeoperation. The servo information is written or encoded onto the discwith a machine commonly referred to as a servo-track writer (STW) thatis removed from the disc drive after the servo writing is completed. Atthe time the servo information is written, the disc drive is typicallyat the “head disk assembly” (HDA) stage. The HDA includes most of themechanical drive components but does not typically include all the driveelectronics. During the track writing process, the STW precisely locatesthe transducer heads relative to the disc surface and writes the servoinformation thereon. Accurate location of the transducer heads isnecessary to ensure that the track definition remains concentric. If theservo track information is written eccentrically, the position of thetransducer head during subsequent operation will require relativelylarge, constant radial adjustments in order to maintain placement overthe track center. When the tracks are sufficiently eccentric, asignificant portion of the disk surface must be allotted for trackmisregistration.

[0008] When the disc drive is manufactured, it is typical to write servotracks on the disc surface in a predetermined pattern as describedabove. The encoded pattern of these servo tracks are later read and usedto move the read/write heads to, and maintain the read/write heads on, adesired track of data. Typically, there will be a slight radial movementrequired to move either the read head or the write head to thecenterline of the desired track. That is, once the position of the trackis determined by reading the servo information, the read head (which wasused to read the servo information) can be positioned to the centerlineof the track, however a separate adjustment of the radial position maybe required if the write head is to be positioned to the centerline ofthe track. The spacing between the read and write heads can vary fromhead to head because of manufacturing variations and differences in theangle which different heads are attached to their respective arms.Further, a rotary actuator moves the read and write heads in an arc,rather than along a radius of the disc, and thus the spacing between theread and write heads will vary depending on the radius of the trackbeing accessed.

[0009] One design goal is to increase the storage capacity of discdrives. One way to increase capacity is to increase the density oftracks on the disc, and the density of date within each track, in orderto save space and reduce the number of discs needed to store aparticular amount of data. Several methods are currently used to storedata on a disc. One method divides the disc surfaces into frequencyzones, and groups one or more contiguous tracks into each frequencyzone. Within each frequency zone, the transducer writes the data ontothe disc at a fixed frequency as the magnetic disc rotates at a fixedangular velocity. The performance (in terms of the maximum frequencythat data can be written and read reliably) of each frequency zone isdetermined, in order to determine the frequency that will be used forthat frequency zone. Typically, a plurality of frequencies are tested,and the highest frequency giving reliable data transfer to all trackswithin the frequency zone is used as the frequency for the entirefrequency zone.

[0010] During manufacture of a disc drive, one or more sectors aretypically discovered that have errors (initial defective sectors). Onespare sector is typically allocated to replace each bad sectorsdiscovered during manufacture. The initial defective sectors are markedas permanently unreadable, and are thereafter never used.

[0011] Disc drives are made more useful by defining the sectors on thedrive using logical block addresses (LBAs). The logical block addressesare sequential sector numbers starting at zero or one and going up to amaximum LBA determined by the nominal capacity of the drive. An LBAprovided to the drive is then translated to a selected disc position,for example, to the cylinder, head, and sector within the selected trackthat the sector will be found.

[0012] The process of reallocating spare sectors are to replacedefective sectors complicates the process of translating LBAs tophysical locations. There is, therefore, a need for a method andapparatus to allocate spare sectors and to translate addresses thatimprove the reliability, available storage space, and performance of adisc drive.

SUMMARY OF THE INVENTION

[0013] The invention provides a disc-drive system that includes a discdrive. The disc drive includes a disc-drive housing and a disc assemblymounted to rotate within the housing. The disc assembly includes atleast a first disc surface having a plurality of zones including apredefined first zone having a plurality of sectors of data and apredefined second zone having a plurality of sectors of data and apredefined third zone having a plurality of sectors of data. The discdrive also includes a first transducer positionable facing the firstdisc surface to transduce data to and from the first zone and the secondzone and the third zone, an address translator that translates a logicalblock address to a position address and a controller operable to controlpositioning of the transducer based on the position address, wherein afirst predetermined number of spare sectors are allocated to the firstzone, and a second predetermined number of spare sectors are allocatedto the second zone and third zone combined.

[0014] In some embodiments of the system, all of the plurality ofsectors of data in the first zone are recorded at a predetermined firstfrequency, all of the plurality of sectors of data in the second zoneare recorded at a predetermined second frequency that is different thanthe first frequency, and all of the plurality of sectors of data in thethird zone are recorded at a predetermined third frequency that isdifferent than the first frequency and different than the secondfrequency.

[0015] In some embodiments of the system, the address translator furthercomprises a logical zone table, and wherein each logical zone includesone or more zones based on a number of defects found in each zone inorder that each logical zone includes a similar number of defects. Insome such embodiments, each logical zone is allocated a number of sparesectors based on the number of defects found in all zones of the logicalzone. In some embodiments, each logical zone only includes contiguouszones.

[0016] In some embodiments, the address translator further comprises alogical zone table formed by iteratively combining a plurality ofcontiguous zones into logical zones in order to create logical zoneseach including a similar number of defects.

[0017] Some embodiments of the system further include aninformation-handling system operatively coupled to transmit data to andfrom the disc drive, an input/output subsystem operatively coupled toinput and output data to the information-handling system, and a memoryoperatively coupled to transmit data to and from theinformation-handling system.

[0018] The invention also provides a method for determining locations ofsectors in a disc drive, comprising steps of (a) allocating a pluralityof zones for data, (b) determining a defect rate in each of theplurality of zones, and (c) allocating spare sectors based on thedetermined defect rates.

[0019] Some embodiments of the method further include a step of (d)forming logical zones based on the determined defect rates, each logicalzone having one or more of the plurality of zones, in order that eachlogical zone has a similar total number of defects.

[0020] In some embodiments of the method, the step (c) of allocatingfurther comprises allocating a number of spare sectors for each logicalzone based on the total number of defects in that logical zone.

[0021] Some embodiments of the method further include steps of (e)forming a logical zone table, the logical zone table having one or morezones in each logical zone, and (f) translating a logical block address(LBA) into a physical address using the logical zone table.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is an exploded view of a disc drive 100 with a multipledisc stack.

[0023]FIG. 2 is a block diagram of an information handling system 200used in some embodiments of the present invention.

[0024]FIG. 3 is a diagram of a disc surface 1341 divided into initialzones.

[0025]FIG. 4 is a diagram of a disc surface 1341 divided into logicalzones.

[0026]FIG. 5 is a flowchart of a disc-drive certification process 500used in some embodiments.

[0027]FIG. 6 is a block diagram of an LBA translator 600.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028] In the following detailed description of the preferredembodiments, reference is made to the accompanying drawings which form apart hereof, and in which are shown, by way of illustration, specificembodiments in which the invention may be practiced. It is to beunderstood that other embodiments may be utilized and structural changesmay be made without departing from the scope of the present invention.

[0029] The invention described in this application is useful for alltypes of disc drives, including magnetic hard-disc drives, optical discdrives, CDROM, writable CDROM, and rewritable CDROM disc drives, ZIPdrives, floppy-disc drives, and any other type of drives, systems ofdrives (such as a “redundant array of inexpensive/independent discdrives,” or RAID, configuration) or other devices, where a storage discassembly is rotated within a housing, and spare sectors are allocated.The invention is useful with many electrical and mechanicalconfigurations of disc drives having either rotary or linear actuation,and embedded or dedicated servo configurations.

[0030] In some embodiments, each sector stored includes an indicationstored in the sector of its own address, i.e., the disc address that thesector's data belongs at. This allows the drive to skip the bad sectorsthat were marked permanently unreadable. Thus, beginning at somestarting point, the disc drive will read all sectors and search until asector is found that includes the address of the desired sector,discarding the other sectors and thus skipping the sectors that weremarked permanently unreadable. Typically, a plurality of such startingpoints are defined, for example, each successive track can define a newstarting point. If the drive is reading sectors that have an addresshigher than the address sought, sectors earlier on that track are readon a subsequent revolution of the disc, or the previous track can beread.

[0031] The translation of an LBA to a physical position location is spedup by keeping a table of such starting points, along with the LBA rangefor the disc area covered by each starting point.

[0032] Additional spare sectors are also typically allocated across thesurface of each disc. During the lifetime of a disc drive, sectors thatwere initially good or error free will begin to show errors, some ofwhich (soft errors) can be corrected using redundant information encodedon the disc, and others of which (hard errors) cannot be corrected. Whena sector gets a hard error (or one or more soft errors), this is calleda “grown defective sector.” To correct for this, the disc drive can finda subsequent spare sector, then copy every sector from the growndefective sector to the sector just preceding the spare sector to itsrespective following sector (the sector with a number one higher), in aprocess called “slipping.” That is, the sector just before the sparesector is copied (moved or slipped) to the spare sector space, thesector two before the spare sector is copied (moved) to the sector spacejust before the spare sector, and so on. The grown defective sector isthen marked as permanently unreadable, and is thereafter ignored. Eachslipped sector will keep its own address, i.e., the address that showswhich data is stored in that space.

[0033]FIG. 1 is an exploded view of one embodiment of the presentinvention, this embodiment showing one type of a disc drive 100 having arotary actuator. The disc drive 100 includes a housing or base 112, anda cover 114. The base 112 and cover 114 form a disc enclosure. Rotatablyattached to the base 112 on an actuator shaft 118 is an actuatorassembly 120. The actuator assembly 120 includes a comb-like structure122 having a plurality of arms 123. Attached to the separate arms 123 onthe comb 122, are load beams or load springs 124. Load beams or loadsprings are also referred to as suspensions. Attached at the end of eachload spring 124 is a slider 126 which carries a magnetic transducer 150.In some embodiments, transducer 150 includes a electromagnetic coilwrite head 97 and a magneto-resistive read head 98. The slider 126 withthe transducer 150 form what is many times called the head. It should benoted that many sliders have one transducer 150 and that is what isshown in the figures. It should also be noted that this invention isequally applicable to sliders having more than one transducer, such aswhat is referred to as an MR or magneto resistive head in which one MRtransducer 150 is generally used for reading and another transducer suchas a coil is generally used for writing. On the end of the actuator armassembly 120 opposite the load springs 124 and the sliders 126 is avoice coil 128.

[0034] Attached within the base 112 is a first magnet 131 and a secondmagnet 130. As shown in FIG. 1, the second magnet 130 is associated withthe cover 114. The first and second magnets 130 and 131, and the voicecoil 128 are the key components of a voice-coil motor which applies aforce to the actuator assembly 120 to rotate it about the actuator shaft118. Also mounted to the base 112 is a spindle motor 132. The spindlemotor 123 includes a rotating portion called spindle hub 133. In thisparticular disc drive, the spindle motor 132 is within hub 133. In FIG.1, a number of discs 134 (one or more; four are shown) are attached tothe spindle hub 133 to form disc assembly 132. One disc recordingsurface 1341 is shown, however each top and bottom surface of each disc134 will typically have a recording surface. In other disc drives, asingle disc or a different number of discs may be attached to the hub.The invention described herein is equally applicable to disc driveswhich have a plurality of discs as well as disc drives that have asingle disc. The invention described herein is also equally applicableto disc drives with spindle motors which are within the hub 133 or underthe hub.

[0035] Some embodiments of disc-drive system 100 further includedata-handling system 200, shown in FIG. 2, operatively coupled to atleast read data from the disc 134. The data-handling system 200 furtherincludes one or more data processors 2004, one or more memories such asrandom access memory 2032 and read-only memory 2034 operatively coupledto each one of the one or more data processors 2004, and at least oneinput/output system 2012-2022 coupled via bus 2010 to at least one ofthe one or more data processors 2004 to receive input data and to supplyoutput data. In FIG. 2, block 2012 is a disc-drive subsystem thatincludes one or more disc drives 100 as described above. In someembodiments, block 2014 is a removable-media subsystem including adiskette drive that reads data from diskette 2001 (or other computerreadable media). In some embodiments, input/output system 2012-2022includes block 2012 that is a graphical user output subsystem, having,for example, a CRT or LCD output display and a display adaptor card,block 2014 that is a user input subsystem, having, for example, akeyboard and/or mouse input device(s), block 2016 that is a networksubsystem, having, for example, a network interface card (NIC) and aconnected network having such devices as a file server, print server,etc., block 2018 that is an internet interface subsystem, having, forexample, a modem connected to a telephone line, DSL router, or cable,block 2020 that is a printer subsystem, and block 2022 that is anexternal device controller subsystem, having, for example, an X10(TM)controller (such as those sold by www.x10.com) for controlling, and/orreceiving information from, external devices such as lamps, videocameras, alarms, motors, video recorders, etc. Some embodiments ofsystem 200 will have all the described I/O devices, and otherembodiments will contain a subset of these devices, or none.

[0036]FIG. 3 is a diagram of a disc surface 1341 divided into initialzones 311-316. A “zone” is a contiguous set of sectors one each of oneor more disc surfaces. In the present invention, a disc drive has aplurality of zones. Each one of the “initial zones” 311-316 can be asingle track under a single head, or can be a contiguous group of one ormore tracks under each of one or more heads (a single track under aplurality of heads is called a “cylinder”). In some embodiments, eachzone is a “frequency zone” (as described above, and having one or moretracks) wherein all the data within a single frequency zone is writtenand read using a single transducing frequency but where differentfrequency zones use different transducing frequencies. In someembodiments, each frequency zone is also called a “physical zone.” Inother embodiments, the disc drive is divided into a plurality ofphysical zones having boundaries that are independent of frequency-zoneboundaries. Thus, a physical zone can be, but need not be, equal to afrequency zone. In some embodiments, a zone is a subset of a trackcontained within a track (e.g., each track can be two zones each havinghalf of the sectors of that track). A zone can also span two or moretracks without being an integer number of tracks. However, making eachinitial zone equal to one track can make the calculations easier, and isused in the following examples for ease of explanation.

[0037] Disc drives incur defects, both during the process ofmanufacturing and also in the field after manufacturing, that make somesectors unusable. The present invention handles such defects by makingspare sectors (“spares”) available. The spare sectors are subtractedfrom the total capacity of the disc drive when defining the nominalcapacity of the drive. For example, if about one percent of the sectorswill be needed for spares, in order to obtain a disc drive with anominal capacity of 40 gigabytes (40 GB), the drive would need a totalphysical capacity of 40.404 GB to provide 0.404 GB of spare sectors plusthe 40 GB nominal capacity. In some embodiments, the present inventionprovides these spare sectors distributed across the disc surface(s).However, the spares are typically not needed in an even distribution,but rather, more spare sectors will be needed where the defect densityis the greatest. Thus, the present invention provides a variable numberof spare sectors per track (VSPT) to assist in defect management.

[0038] The present invention forms logical zones, each logical zonecombining one or more of the initial zones. These logical zones form onebasis for allocating spare sectors. As an example, a drive can bemanufactured with a thousand (1000) physical sectors per track. With onepercent (1%) allocated for spares, the drive will have (990) logicalsectors per track, and ten (10) spare sectors per track. However, 10 insome drives, some tracks will experience more than ten initial defectivesectors, and thus have fewer than (990) logical sectors, and others mayhave more than (990) available sectors. This variable number of sectorsmakes the calculation that converts an LBA into a cylinder-head-sectoraddress complicated.

[0039]FIG. 4 is a diagram of a disc surface 1341 divided into threelogical zones 411, 412, and 413. Logical zone 411 includes initial zones311, 312, and 313, logical zone 412 includes initial zones 314, andlogical zone 413 includes initial zones 315 and 316. In someembodiments, the logical zones 411-413 are formed using as process asdescribed below.

[0040] A key element of the variable spares per track (VSPT) defectmanagement scheme of the present invention is the logical zone table(LZT). The LZT sub-divides each physical zone (or combines one or moreinitial zones) into logical zones (or partitions) that contain tracksaffected by a similar defect distribution on the media. In doing so, aconstant number of logical sectors per track is achieved for aparticular logical zone, in some embodiments. By having the same numberof logical sectors on every track within a logical zone, the calculationof a cylinder-head-sector address from an LBA is simplified. As aresult, the tedious logical block address (LBA) to physicalcylinder/head/sector (PCHS) translation process in full-slip defectmanagement is avoided. In full-slip defect management, the movement ofdata can span multiple tracks, possibly resulting in differing numbersof logical sectors per track among the involved tracks, and thus the LBAtranslation that only calculated the initial LBA mapping to the initialsector on each track needs to be supplemented by additional calculationsor sector searching once a defective sector and all other sectorsbetween the defect and the spare sector are “slipped” one sector over.

[0041]FIG. 5 shows a disc-drive certification process 500. In someembodiments, the LZT generation process 560 is incorporated after thedefect detection test stage 550 of the disc-drive certification process500. Servo information is written to the disc surface(s) at stage 510.The disc surfaces are then pretested with various write and readoperations at stage 520. A servo-test stage 530 verifies and/orcalibrates the information.

[0042] The read write tuning stage 540, calibrates the read-write-chipsystem with parameters optimized for reads and writes, for example,providing a plurality of frequency zones that each use read or writefrequencies. Upon completion of this stage, the defect test stage 550scans the entire media and maps out defective sectors found into thedrive's defect table. The defect table indicates the physical locationof defective sectors on each track of the drive.

[0043] Stage 560 creates a logical zone table (LZT). Since the LZT isgenerated after all known defects have been captured, spares sectors canbe allocated efficiently since the defect distribution on the drive hasalready been determined.

[0044] LZT Generation Algorithm

[0045] For some embodiments, the objectives of the LZT algorithm are asfollows:

[0046] Allocate spares for each defective sector efficiently.

[0047] Minimize spares redundancy (where spares redundancy refers to theprovision of more spares than actual defects present).

[0048] Partition each physical zone until there are MAX_LOGICALZONES orfewer logical zones per physical zone.

[0049] Ensure enough spares are allocated for grown defects, and thatsuch spares are allocated uniformnly with respect to the expected needacross the disc surface. Spares are allocated where they will be used.Thus, areas in which more defects are initially detected are expected tohave more grown defects, and will be allocated more spares, while areashaving fewer initially detected defects are expected to incur fewergrown defects, and thus will be allocated fewer spares.

[0050] The algorithm comprises two sub-processes:

[0051] Logical Zone Partition 560

[0052] Spares Allocation 570

[0053] Logical Zone Partition Process

[0054] The logical zone partition process is an iterative process. Itsobjective is to minimize the redundancy created when cylinders arepartitioned into logical zones. The algorithm can be expressedmathematically as follows:${{Total}\quad {{no}.\quad {of}}\quad {defects}\quad {in}\quad {TLZ}_{k}^{i}} = {\sum\limits_{n \in {TLZ}_{k}^{i}}{D(n)}}$${{Total}\quad {{no}.\quad {of}}\quad {spares}\quad {allocated}} = {( {\max\limits_{n \in {TLZ}_{k}^{i}}\lbrack {D(n)} \rbrack} ) \cdot t_{k}^{i}}$${{Total}\quad {redundancy}\quad {on}\quad {all}\quad {heads}\quad {in}\quad {TLZ}_{k}^{i}} = {\sum\limits_{heads}\{ {{( {\max\limits_{n \in {TLZ}_{k}^{i}}\lbrack {D(n)} \rbrack} ) \cdot t_{k}^{i}} - {\sum\limits_{n \in {TLZ}_{k}^{i}}{D(n)}}} \}}$

[0055] For each iteration, the algorithm identifies the minimumredundancy TLZ_(k) ^(i) which now forms a part of the set of alltentative logical zones for the next iteration. Iteration terminateswhen the number of tentative zones are less than or equal toMAX_LOGICALZONES.$\min\limits_{{TLZ}_{k}^{i} \in Z^{i}}\{ {\sum\limits_{heads}\{ {{( {\max\limits_{n \in {TLZ}_{k}^{i}}\lbrack {D(n)} \rbrack} ) \cdot t_{k}^{i}} - {\sum\limits_{n \in {TLZ}_{k}^{i}}{D(n)}}} \}} \}$

[0056] D(n): Defect distribution function of drive. e.g. if track 100has 5 defective sectors, D(100)=5.

[0057] Z^(i): Set of all tentative logical zones in iteration i.

[0058] TLZ_(k) ^(i): k-th tentative logical zone of iteration i

[0059] tk^(i): Number of tracks in the k-th tentative logical zone ofiteration i

[0060] n: Track number

[0061] To illustrate this process, an example is given of a two-headdrive with six (6) cylinders and the following defect distribution tableas shown in Table 1a below. Each initial zone will have one cylinder.Each track has 1000 sectors and since there are 12 tracks, the totalphysical capacity of the drive is 12000 sectors. In this example, 1.0%of the physical capacity (120 sectors) is allocated for defects, hencethe logical capacity of the drive is 11880 sectors (12 tracks times 990sectors per track). Also, MAX_LOGICALZONES is set to three (3). Thus,the algorithm will combine the six initial zones into three (or fewer)logical zones. In this drive, all six initial zones will be in a singlephysical zone, however other embodiments will have a plurality ofphysical zones, each having up to three logical zones. TABLE 1a CylinderDefects/Track 1 2 3 4 5 6 Head 0 8 3 4 20 3 6 Head 1 2 9 7 2 9 14

[0062] Referring again to FIG. 3, but using a single disc platter, inthis example cylinder 1 would correspond to initial zone 311 includingboth the top surface 1341 under a “head 0” and an opposing bottomsurface transduced by a “head 1.” Similarly, cylinder 2 would correspondto initial zone 312, cylinder 3 would correspond to initial zone 313,cylinder 4 would correspond to initial zone 314, cylinder 5 wouldcorrespond to initial zone 315, and cylinder 6 would correspond toinitial zone 316.

[0063] At stage A, temporary (or tentative) logical zones (TLZs) areassigned such that each cylinder is a separate initial zone. Theresulting stage-A TLZ Table (with 6 TLZs) is shown in Table 1b. TABLE 1bCylinder Initial TLZ Table 1 2 3 4 5 6 Initial Zone # = TLZ 1 2 3 4 5 6

[0064] During stage B, each TLZ is virtually merged with its adjacentTLZ, e.g., TLZ1 and TLZ2, TLZ2 and TLZ3, etc. For each virtual mergedzone, the following parameters are computed:

[0065] No. of Tracks->the number of tracks within the merged zoneboundary.

[0066] Max Defect Per Track->the maximum number of defects that werefound in any one track in the merged temporary zone.

[0067] Total Defects->the total number of defective sectors on aparticular head within the merged zone boundary.

[0068] Redundancy->the difference between the total spares allocated andthe total number of defects present on a particular head within themerged zone boundary.

Redundancy=(No. of tracks×Max Defects Per Track)−Total Defects  (1)

[0069] Total Redundancy->sum total of the redundancies per head.$\begin{matrix}{{{Total}\quad {redundancy}} = {\sum\limits_{i}^{head}{redundancy}_{i}}} & (2)\end{matrix}$

[0070] Table 2 below shows the computed stage B results which indicatethat merging TLZ2 and TLZ3 yields the lowest total redundancy. As such,TLZs 2 and 3 are now physically merged to yield TLZ2. TABLE 2 TentativeLogical  1 2  3  4 5 Zone = TLZ′ Merged temporary 1-2 2-3 3-4 4-5 5-6zone Cylinders in MTZ 1-2 2-3 3-4 4-5 5-6 (= initial zones) Number oftracks in  2 2  2  2 2 MTZ = “a” Head 0 1 0 1 0 1 0 1 0 1 Maximumdefects per 8 9 4 9 20 7 20 9 6 14 track in MTZ = “b” Total defects ineach 11 11 7 16 24 9 23 11 9 23 MTZ = “c” Redundancy = “d” = 5 7 1 2 165 17 7 3 5 (a*b) − c Total redundancy = d 12 3 21 24 8 (head 0) +d(head 1) Choice for merge after ***** this iteration

[0071] The combined initial zones 2 and 3 are thus combined, and theremaining zones are left alone. The remaining TLZs are re-orderedaccordingly and the resulting new stage B TLZ Table (with 5 TLZs) isshown in Table 2b. TABLE 2b New temporary zone number 1′ 2′ 3′ 4′ 5′Cylinders 1 2-3 4 5 6

[0072] Next, at stage C, each TLZ in the new stage B TLZ Table is againvirtually merged with its adjacent TLZ. Table 3a below shows thecomputed stage C results which indicate that merging TLZ4 and TLZ5yields the lowest total redundancy. As such, TLZs 4 and 5 are merged toyield TLZ4. TABLE 3a Tentative Logical Zone 1″ 2″ 3″ 4″ Merged temporaryzone 1′-2′ 2′-3′ 3′-4′ 4′-5′ Cylinders in MTZ 1-3 2-4 4-5 5-6 (= initialzones) Number of tracks in MTZ = “a”  3  3  2 2 Head 0 1 0 1 0 1 0 1Maximum defects per track in 8 9 20 9 20 9 6 14 MTZ = “b” Total defectsin each MTZ = “c” 15 18 27 18 23 11 9 23 Redundancy = “d” = 9 9 33 9 177 3 5 (a*b) − c Total redundancy = 18 42 24 8 d(head 0) + d(head 1)Choice for merge after ***** this iteration

[0073] The remaining TLZs are again re-ordered accordingly and theresulting new stage C TLZ Table (with 4 TLZs) is shown in Table 3b.TABLE 3b New temporary zone number 1″ 2″ 3″ 4″ Cylinders 1 2-3 4 5-6

[0074] Finally, during stage D, the merging process is again repeated.Table 4a below shows the computed stage D results which indicate thatmerging TLZ1 and TLZ2 yields the lowest total redundancy. As such, TLZs1 and 2 are merged to yield TLZ1. TABLE 4a Tentative Logical Zone 1′″2′″ 3′″ Merged temporary zone 1″-2″ 2″-3″ 3″-4″ Cylinders in MTZ (=initial zones) 1-3 2-4 4-6 Number of tracks in MTZ = “a”  3  3  3 Head 01 0 1 0 1 Maximum defects per track in MTZ = “b” 8 9 20 9 20 14 Totaldefects in each MTZ = “c” 15 18 27 18 29 25 Redundancy = “d” = (a*b) − c9 9 33 9 31 17 Total redundancy = d(head 0) + d(head 1) 18 42 48 Choicefor merge after this iteration *****

[0075] The remaining TLZs are again re-ordered accordingly and theresulting new stage D TLZ Table (with 3 TLZs) is shown in Table 4b.TABLE 4b New temporary zone number =  1′′′  2′′′  3′′′ the final logicalzone number in this case 1 2 3 Cylinders 1-3 4 5-6

[0076] Referring again to FIG. 4, but using a single disc platter, inthis example final logical zone number 1 (temporary zone 1′″) wouldcorrespond to logical zone 411 including both the top surface 1341 undera “head 0” and an opposing bottom surface transduced by a “head 1.”Similarly, final logical zone number 2 would correspond to logical zone412, and final logical zone number 3 would correspond to logical zone413.

[0077] For this example, since the maximum number of logical zones perphysical zone (MAX_LOGICALZONES) is 3, the algorithm terminates with thelogical zone cylinder boundaries determined. Table 5 is the interimlogical zone table generated, with the assumption that there are 1000physical sectors per track. TABLE 5 Interim Logical Zone Table The finallogical zone number 1 2 3 in this case Starting Cylinder 1 4 5 Cylindersin LZ 1-3 4 5-6 (= initial zones) Number of tracks in 3 1 2 MTZ = “a”Head 0 1 0 1 0 1 Maximum defects per track 8 9 20 2 6 14 in MTZ = “b”Logical Sectors Per 992 991 980 998 994 986 Track = 1000 − b Redundancyper Logical 9 9 0 0 3 5 Zone per head

[0078] In other embodiments, there are more than one physical zone, andwithin each physical zone the above process is performed. The number ofiterations will vary according to the value set for MAX_LOGICALZONES,which can differ from three, the value used in this example. Further,some of the plurality of physical zones can have a different number ofinitial zones, and thus a given number of iterations will result invarying numbers of final logical zones.

[0079] Spares Allocation Process

[0080] After the logical zone partition process is completed, the sparesallocation process is initiated to allocate the remaining spares to thepartitioned logical zones for grown defects. Beginning with the logicalzone with the least redundancy, the algorithm proceeds to distribute theremaining spares to the logical zones. When the spares are exhausted, orwhen insufficient number of spares are available for allocation, thealgorithm would terminate.

[0081] Here is an example based on the interim logical zone tablegenerated earlier. The first stage of the spares allocation phase of theLZT generation algorithm, determines the number of spares for growndefects previously allocated (which also equals the redundancy of thatzone) during the logical zone partition process. The resultingallocation matrix is shown in Table 6 below. The allocation matrix showsthat LZ2 head 0 and 1 have the least redundancy and LZ1 heads 0 and 1the most. TABLE 6 Extra Spares Allocation Matrix The final logical zonenumber in this case 1 2 3 Redundancy per Logical Zone per head 9 9 0 0 35

[0082] Next, the number of spares remaining for allocation is calculatedas follows: $\begin{matrix}{{{Spares}\quad {for}\quad {Allocation}} = \quad {{{Total}\quad {Physical}\quad {Capacity}} -}} \\{\quad {{{Logical}\quad {Capacity}} - {{Factory}\quad {Defects}} -}} \\{\quad {{Spares}\quad {Allocated}\quad {By}\quad {LZT}\quad {Generation}\quad (3)}} \\{= \quad {6\quad {cylinders}*1000\quad {{sectors}/{track}}*}} \\{\quad {{2\quad {{tracks}/{cylinder}}} - {6*990*2} - 87 - 26}} \\{= \quad {12000 - 11880 - 113}} \\{= \quad {7\quad {remaining}\quad {sectors}\quad {for}\quad {the}\quad {final}\quad {allocation}}}\end{matrix}$

TABLE 7 Allocation of Final Spares to Logical Zone Table The finallogical zone number 1 2 3 Head Remaining 0 1 0 1 0 1 Sectors StageInitial 992 991 980 998 994 986 7 I Logical Sectors Per Track LogicalSectors Per Track 992 991 979 998 994 986 6 II Logical Sectors Per Track992 991 979 997 994 986 5 III Logical Sectors Per Track 992 991 979 997993 986 3 IV Logical Sectors Per Track 992 991 979 997 993 985 1 VLogical Sectors Per Track 992 991 979 997 993 985 1 VI Logical SectorsPer Track 992 991 979 997 993 985 1 VII Final 992 991 978 997 993 985 0VIII Logical Sectors Per Track

[0083] Table 7 above contains a snapshot of the logical sectors pertrack of each zone during the different stages of the spares allocationalgorithm. At stage I, no spares have been allocated yet, and thelogical sectors per track are as per Table 5.

[0084] From Table 6, as LZ2/Hd0 has the smallest redundancy, so 1 spareper track is allocated to it. As shown in Table 7 stage II, the logicalsectors per track are reduced by one to 979, and the spares remaining is6. In stage III, LZ2/Hd1 has the next smallest redundancy and it isallocated one spare per track and the logical sectors per track andspares remaining updated. In stage IV, LZ3/Hd0 is allocated next andrequires 2 spares as the zone spans across two tracks 5 and 6. In stageV, LZ3/Hd1 is allocated and again requires 2 spares. The number ofspares remaining is now one. At stage VI, the algorithm determines thatLZ1/Hd0 requires 3 spares but the only one spare remains, so noallocation takes place. Similarly at stage VII, the algorithm againdetermines that LZ1/Hd1 requires 3 spares so no allocation is done.

[0085] Finally, at stage VIII, the algorithm has attempted to allocatedspares to all logical zones and thus repeats the process at LZ1/Hd0.Since this zone requires 1 spare and there is one remaining spare,allocation takes place and the zones logical sectors per track isupdated as shown. The algorithm is then terminated here as there are noremaining spares left. However, if there were sufficient spares, thealgorithm would proceed until no spares are left or no logical zones canbe allocated with spares completely.

[0086] In this way, the above spare allocation process helps to ensurethat there is at least one local spare within each track for growndefects.

[0087] Further, the translation from LBA to cylinder-head-sector issimplified, in that all tracks within a logical zone have the samenumber of logical sectors, thus once the logical zone containing the LBAis found (e.g., by comparing the LBA to the initial and/or final LBA ofeach zone), the remainder (e.g., by subtracting the LBA from the initialLBA of a logical zone) can be divided by the number of logical sectorsper track to find the track/cylinder number and head number.

[0088] As an example, Table 8 below provides one example of a resultingLogical Zone table that can be used in translating an LBA into acylinder-head-sector address using logical zones. In this example, LBAsare mapped to consecutive sectors under one head, then the next head,and so on to the last logical sector of the drive. TABLE 8 Example of aLogical Zone Table Logical zone 1 2 3 number Starting Cylinder 1 4 5Head  0  1  0  1  0  1 Final 992 991 978 997 993 985 Logical Sectors PerTrack Starting LBA  0 2976 = 5949 = 6927 = 7924 = 9910 = 3*992 3*992 +3*992 + 3*992 + 3*992 + 3*991 3*991 + 3*991 + 3*991 + 1*978 1*978 +1*978 + 1*997 1*997 + 2*993

[0089] In this example, the last LBA will be LBA sector number 11879.The first logical zone covers LBA=0 to LBA=5948, where head 0 cylinders1, 2, and 3 include LBA=0 to LBA=2975, and head 1 cylinders 1, 2, and 3include LBA=2976 to LBA=5948, all of which are in logical zone 1. ThusLBAs 0 to 5948 are mapped to logical zone 1, then to the proper head andcylinder, and a seek moves the transducer 150 to the correspondingposition and then sectors are read from that head and cylinder until thecorrect sector is (or sectors are) found.

[0090]FIG. 6 is a block diagram of an LBA translator 600. Block 610performs the LBA translation to cylinder-head-sector, controller 620moves the arm to the position desired, and arm/transducer 630 reads datafrom the selected track until the desired data sector(s) is found.

[0091] Conclusion

[0092] The Logical Zone Table (LZT) generation process has beendescribed. It consists of two sub-processes; the logical zone partitionprocess and the spares allocation process. Each logical zone in the LZTgenerated contains tracks affected by a similar defect distribution onthe media and has a constant number of logical sectors per track. Thisallows the tedious logical block address (LBA) to physicalcylinder/head/sector (PCHS) translation process in full slip defectmanagement to be avoided completely.

[0093] The disc drive 100 of FIG. 1 includes a disc-drive housing 112,114 and a disc assembly 134 mounted to rotate within the housing. Thedisc assembly 134 includes at least a first disc surface 1341 having aplurality of zones including a predefined first zone having a pluralityof sectors of data and a predefined second zone having a plurality ofsectors of data and a predefined third zone having a plurality ofsectors of data. The disc drive also includes a first transducer 150/630positionable facing the first disc surface to transduce data to and fromthe first zone 314 and the second zone 315 and the third zone 316, anaddress translator 610 that translates a logical block address to aposition address and a controller 620 operable to control positioning ofthe transducer based on the position address, wherein a firstpredetermined number of spare sectors are allocated to the first zone,and a second predetermined number of spare sectors are allocated to thesecond zone and third zone combined.

[0094] In some embodiments of the system, all of the plurality ofsectors of data in the first zone are recorded at a predetermined firstfrequency, all of the plurality of sectors of data in the second zoneare recorded at a predetermined second frequency that is different thanthe first frequency, and all of the plurality of sectors of data in thethird zone are recorded at a predetermined third frequency that isdifferent than the first frequency and different than the secondfrequency.

[0095] In some embodiments of the system, the second predeterminednumber of spare sectors is based on a number of defects found in thesecond zone and third zone combined, and the first predetermined numberof spare sectors is based on a number of defects found in the firstzone.

[0096] In some embodiments of the system, the address translator furthercomprises a logical zone table, wherein the first zone is located in afirst logical zone, and the second zone and third zone are both locatedin a second logical zone.

[0097] In some embodiments of the system, the address translator furthercomprises a logical zone table, and wherein each logical zone includesone or more zones based on a number of defects found in each zone inorder that each logical zone includes a similar number of defects. Insome such embodiments, each logical zone is allocated a number of sparesectors based on the number of defects found in all zones of the logicalzone. In some embodiments, each logical zone only includes contiguouszones.

[0098] In some embodiments, the address translator further comprises alogical zone table formed by iteratively combining a plurality ofcontiguous zones into logical zones in order to create logical zoneseach including a similar number of defects.

[0099] Some embodiments of the system further include aninformation-handling system operatively coupled to transmit data to andfrom the disc drive, an input/output subsystem operatively coupled toinput and output data to the information-handling system, and a memoryoperatively coupled to transmit data to and from theinformation-handling system.

[0100] Another aspect of the present invention provides a method fordetermining locations of sectors in a disc drive, comprising steps of(a) allocating a plurality of zones for data, (b) determining a defectrate in each of the plurality of zones, and (c) allocating spare sectorsbased on the determined defect rates.

[0101] Some embodiments of the method further include a step of (d)forming logical zones based on the determined defect rates, each logicalzone having one or more of the plurality of zones, in order that eachlogical zone has a similar total number of defects.

[0102] In some embodiments of the method, the step (c) of allocatingfurther comprises allocating a number of spare sectors for each logicalzone based on the total number of defects in that logical zone.

[0103] Some embodiments of the method further include steps of (e)forming a logical zone table, the logical zone table having one or morezones in each logical zone, and (f) translating a logical block address(LBA) into a physical address using the logical zone table.

[0104] In some embodiments of the method, all the zones in each logicalzone having more than one zone are contiguous zones.

[0105] Some embodiments of the method further include steps of (g)forming a logical zone table, the logical zone table initially havingtwo or more contiguous zones in each tentative logical zone, (h)determining which one of the tentative logical zones has the fewesttotal defects, and combining the zones forming that tentative logicalzone having the fewest total defects into a single zone, while leavingthe other zones as separate, and (i) iteratively repeating steps (g) and(h).

[0106] Some embodiments of the method further include steps of (j)iteratively combining the zones into logical zones in order to obtainlogical zones each having a similar number of defects, (k) allocatingspare sectors to each logical zone based on a number of defects in eachrespective logical zone, and (l) translating logical block addressesbased on the logical zones.

[0107] In some embodiments of the method, each one of the plurality ofzones uses a single transducing frequency that is different than thesingle transducing frequency of the other zones.

[0108] Some embodiments of the method further include steps of (m)iteratively combining the zones into logical zones in order to obtainlogical zones each having a similar number of defects, (n) allocating anequal number of spare sectors to each logical zone, and (o) translatinglogical block addresses based on the logical zones.

[0109] Yet another aspect of the present invention provides a disc drivesystem that includes a rotating disc having a plurality of zones of dataincluding a first zone, a second zone, and a third zone, a transducerpositionable to transduce data to the first, second, and third zones,and means for allocating spare sectors to the first, second, and thirdzones and for translating logical block addresses to physical addressesbased on the allocation of spare sectors.

Conclusion

[0110] Described above is a method and apparatus for generating logicalzones that each have an effective or optimized number of spare sectors.

[0111] In some embodiments, the invention provides a disc-drive systemthat includes a disc drive. The disc drive includes a disc-drive housingand a disc assembly mounted to rotate within the housing. The discassembly includes at least a first disc surface having a plurality ofzones including a predefined first zone having a plurality of sectors ofdata and a predefined second zone having a plurality of sectors of dataand a predefined third zone having a plurality of sectors of data. Thedisc drive also includes a first transducer positionable facing thefirst disc surface to transduce data to and from the first zone and thesecond zone and the third zone, an address translator that translates alogical block address to a position address and a controller operable tocontrol positioning of the transducer based on the position address,wherein a first predetermined number of spare sectors are allocated tothe first zone, and a second predetermined number of spare sectors areallocated to the second zone and third zone combined.

[0112] In some embodiments of the system, all of the plurality ofsectors of data in the first zone are recorded at a predetermined firstfrequency, all of the plurality of sectors of data in the second zoneare recorded at a predetermined second frequency that is different thanthe first frequency, and all of the plurality of sectors of data in thethird zone are recorded at a predetermined third frequency that isdifferent than the first frequency and different than the secondfrequency.

[0113] In some embodiments of the system, the second predeterminednumber of spare sectors is based on a number of defects found in thesecond zone and third zone combined, and the first predetermined numberof spare sectors is based on a number of defects found in the firstzone.

[0114] In some embodiments of the system, the address translator furthercomprises a logical zone table, wherein the first zone is located in afirst logical zone, and the second zone and third zone are both locatedin a second logical zone.

[0115] In some embodiments of the system, the address translator furthercomprises a logical zone table, and wherein each logical zone includesone or more zones based on a number of defects found in each zone inorder that each logical zone includes a similar number of defects. Insome such embodiments, each logical zone is allocated a number of sparesectors based on the number of defects found in all zones of the logicalzone. In some embodiments, each logical zone only includes contiguouszones.

[0116] In some embodiments, the address translator further comprises alogical zone table formed by iteratively combining a plurality ofcontiguous zones into logical zones in order to create logical zoneseach including a similar number of defects.

[0117] Some embodiments of the system further include aninformation-handling system operatively coupled to transmit data to andfrom the disc drive, an input/output subsystem operatively coupled toinput and output data to the information-handling system, and a memoryoperatively coupled to transmit data to and from theinformation-handling system.

[0118] Another aspect of the present invention provides a method fordetermining locations of sectors in a disc drive, comprising steps of(a) allocating a plurality of zones for data, (b) determining a defectrate in each of the plurality of zones, and (c) allocating spare sectorsbased on the determined defect rates.

[0119] Some embodiments of the method further include a step of (d)forming logical zones based on the determined defect rates, each logicalzone having one or more of the plurality of zones, in order that eachlogical zone has a similar total number of defects.

[0120] In some embodiments of the method, the step (c) of allocatingfurther comprises allocating a number of spare sectors for each logicalzone based on the total number of defects in that logical zone.

[0121] Some embodiments of the method further include steps of (e)forming a logical zone table, the logical zone table having one or morezones in each logical zone, and (f) translating a logical block address(LBA) into a physical address using the logical zone table.

[0122] In some embodiments of the method, all the zones in each logicalzone having more than one zone are contiguous zones.

[0123] Some embodiments of the method further include steps of (g)forming a logical zone table, the logical zone table initially havingtwo or more contiguous zones in each tentative logical zone, (h)determining which one of the tentative logical zones has the fewesttotal defects, and combining the zones forming that tentative logicalzone having the fewest total defects into a single zone, while leavingthe other zones as separate, and (i) iteratively repeating steps (g) and(h).

[0124] Some embodiments of the method further include steps of (j)iteratively combining the zones into logical zones in order to obtainlogical zones each having a similar number of defects, (k) allocatingspare sectors to each logical zone based on a number of defects in eachrespective logical zone, and (l) translating logical block addressesbased on the logical zones.

[0125] In some embodiments of the method, each one of the plurality ofzones uses a single transducing frequency that is different than thesingle transducing frequency of the other zones.

[0126] Some embodiments of the method further include steps of (m)iteratively combining the zones into logical zones in order to obtainlogical zones each having a similar number of defects, (n) allocating anequal number of spare sectors to each logical zone, and (o) translatinglogical block addresses based on the logical zones.

[0127] Yet another aspect of the present invention provides a disc drivesystem that includes a rotating disc having a plurality of zones of dataincluding a first zone, a second zone, and a third zone, a transducerpositionable to transduce data to the first, second, and third zones,and means for allocating spare sectors to the first, second, and thirdzones and for translating logical block addresses to physical addressesbased on the allocation of spare sectors.

[0128] It is to be understood that the above description is intended tobe illustrative, and not restrictive. Although numerous characteristicsand advantages of various embodiments of the present invention have beenset forth in the foregoing description, together with details of thestructure and function of various embodiments, many other embodimentsand changes to details will be apparent to those of skill in the artupon reviewing the above description. The scope of the invention should,therefore, be determined with reference to the appended claims, alongwith the full scope of equivalents to which such claims are entitled.

What is claimed is:
 1. A disc-drive system comprising: a disc drive, thedisc drive including: a disc-drive housing; a disc assembly mounted torotate within the housing, the disc assembly including at least a firstdisc surface having a plurality of zones including a predefined firstzone having a plurality of sectors of data and a predefined second zonehaving a plurality of sectors of data and a predefined third zone havinga plurality of sectors of data; a first transducer positionable facingthe first disc surface to transduce data to and from the first zone andthe second zone and the third zone; an address translator thattranslates a logical block address to a position address and acontroller operable to control positioning of the transducer based onthe position address, wherein a first predetermined number of sparesectors are allocated to the first zone, and a second predeterminednumber of spare sectors are allocated to the second zone and third zonecombined.
 2. The system according to claim 1, wherein all of theplurality of sectors of data in the first zone are recorded at apredetermined first frequency, all of the plurality of sectors of datain the second zone are recorded at a predetermined second frequency thatis different than the first frequency, and all of the plurality ofsectors of data in the third zone are recorded at a predetermined thirdfrequency that is different than the first frequency and different thanthe second frequency.
 3. The system according to claim 1, wherein thesecond predetermined number of spare sectors is based on a number ofdefects found in the second zone and third zone combined, and the firstpredetermined number of spare sectors is based on a number of defectsfound in the first zone.
 4. The system according to claim 1, wherein theaddress translator further comprises a logical zone table, wherein thefirst zone is located in a first logical zone, and the second zone andthird zone are both located in a second logical zone.
 5. The systemaccording to claim 1, wherein the address translator further comprises alogical zone table, and wherein each logical zone includes one or morezones based on a number of defects found in each zone in order that eachlogical zone includes a similar number of defects.
 6. The systemaccording to claim 5, wherein each logical zone is allocated a number ofspare sectors based on the total number of defects found in all of thezones of the logical zone.
 7. The system according to claim 5, whereineach logical zone only includes one or more contiguous zones.
 8. Thesystem according to claim 1, wherein the address translator furthercomprises a logical zone table formed by iteratively combining aplurality of contiguous zones into logical zones in order to createlogical zones each including a similar number of defects.
 9. The systemaccording to claim 1, further comprising: an information-handling systemoperatively coupled to transmit data to and from the disc drive; aninput/output subsystem operatively coupled to input and output data tothe information-handling system; and a memory operatively coupled totransmit data to and from the information-handling system.
 10. A methodfor determining locations of sectors in a disc drive, comprising stepsof: (a) allocating a plurality of zones for data; (b) determining adefect rate in each of the plurality of zones; and (c) allocating sparesectors based on the determined defect rates.
 11. The method accordingto claim 10, further comprising a step of: (d) forming logical zonesbased on the determined defect rates, each logical zone having one ormore of the plurality of zones, in order that each logical zone has asimilar total number of defects.
 12. The method according to claim 11,wherein the step (c) of allocating further comprises allocating a numberof spare sectors for each logical zone based on the total number ofdefects in that logical zone.
 13. The method according to claim 12,further comprising steps of: (e) forming a logical zone table, thelogical zone table having one or more zones in each logical zone; and(f) translating a logical block address (LBA) into a physical addressusing the logical zone table.
 14. The method according to claim 11,wherein all the zones in each logical zone having more than one zone arecontiguous zones.
 15. The method according to claim 11, furthercomprising steps of: (g) forming a logical zone table, the logical zonetable initially having two or more contiguous zones in each tentativelogical zone; (h) determining which one of the tentative logical zoneshas the fewest total defects, and combining the zones forming thattentative logical zone having the fewest total defects into a singlezone, while leaving the other zones as separate; and (i) iterativelyrepeating steps (g) and (h).
 16. The method according to claim 11,further comprising steps of: (j) iteratively combining the zones intological zones in order to obtain logical zones each having a similarnumber of defects; (k) allocating spare sectors to each logical zonebased on a number of defects in each respective logical zone; and (l)translating logical block addresses based on the logical zones.
 17. Themethod according to claim 10, wherein each one of the plurality of zonesuses a single transducing frequency that is different than the singletransducing frequency of the other zones.
 18. The method according toclaim 11, further comprising steps of: (m) iteratively combining thezones into logical zones in order to obtain logical zones each having asimilar number of defects; (n) allocating an equal number of sparesectors to each logical zone; and (o) translating logical blockaddresses based on the logical zones.
 19. The method according to claim16, wherein all the zones in each logical zone having more than one zoneare contiguous zones.
 20. A disc drive system comprising: a rotatingdisc having a plurality of zones of data including a first zone, asecond zone, and a third zone; a transducer positionable to transducedata to the first, second, and third zones; and means for allocatingspare sectors to the first, second, and third zones and for translatinglogical block addresses to physical addresses based on the allocation ofspare sectors.